Note
This tutorial can be used interactively with Google Colab! You can also click here to run the Jupyter notebook locally.
Auto-tuning a Convolutional Network for ARM CPU¶
Author: Lianmin Zheng, Zhao Wu, Eddie Yan
Auto-tuning for a specific ARM device is critical for getting the best performance. This is a tutorial about how to tune a whole convolutional network.
The operator implementation for ARM CPU in TVM is written in template form. The template has many tunable knobs (tile factor, vectorization, unrolling, etc). We will tune all convolution and depthwise convolution operators in the neural network. After tuning, we produce a log file which stores the best knob values for all required operators. When the TVM compiler compiles these operators, it will query this log file to get the best knob values.
We also released pre-tuned parameters for some arm devices. You can go to ARM CPU Benchmark to see the results.
Note that this tutorial will not run on Windows or recent versions of macOS. To
get it to run, you will need to wrap the body of this tutorial in a if
__name__ == "__main__": block.
Install dependencies¶
To use the autotvm package in tvm, we need to install some extra dependencies. (change “3” to “2” if you use python2):
pip3 install --user psutil xgboost tornado cloudpickle
To make TVM run faster during tuning, it is recommended to use cython as FFI of TVM. In the root directory of TVM, execute (change “3” to “2” if you use python2):
pip3 install --user cython
sudo make cython3
Now return to python code. Import packages.
import os
import numpy as np
import tvm
from tvm import relay, autotvm
import tvm.relay.testing
from tvm.autotvm.tuner import XGBTuner, GATuner, RandomTuner, GridSearchTuner
from tvm.contrib.utils import tempdir
import tvm.contrib.graph_executor as runtime
Define network¶
First we need to define the network in relay frontend API.
We can load some pre-defined network from relay.testing.
We can also load models from MXNet, ONNX and TensorFlow.
def get_network(name, batch_size):
"""Get the symbol definition and random weight of a network"""
input_shape = (batch_size, 3, 224, 224)
output_shape = (batch_size, 1000)
if "resnet" in name:
n_layer = int(name.split("-")[1])
mod, params = relay.testing.resnet.get_workload(
num_layers=n_layer, batch_size=batch_size, dtype=dtype
)
elif "vgg" in name:
n_layer = int(name.split("-")[1])
mod, params = relay.testing.vgg.get_workload(
num_layers=n_layer, batch_size=batch_size, dtype=dtype
)
elif name == "mobilenet":
mod, params = relay.testing.mobilenet.get_workload(batch_size=batch_size)
elif name == "squeezenet_v1.1":
mod, params = relay.testing.squeezenet.get_workload(
batch_size=batch_size, version="1.1", dtype=dtype
)
elif name == "inception_v3":
input_shape = (batch_size, 3, 299, 299)
mod, params = relay.testing.inception_v3.get_workload(batch_size=batch_size, dtype=dtype)
elif name == "mxnet":
# an example for mxnet model
from mxnet.gluon.model_zoo.vision import get_model
block = get_model("resnet18_v1", pretrained=True)
mod, params = relay.frontend.from_mxnet(block, shape={"data": input_shape}, dtype=dtype)
net = mod["main"]
net = relay.Function(
net.params, relay.nn.softmax(net.body), None, net.type_params, net.attrs
)
mod = tvm.IRModule.from_expr(net)
else:
raise ValueError("Unsupported network: " + name)
return mod, params, input_shape, output_shape
Start RPC Tracker¶
TVM uses RPC session to communicate with ARM boards. During tuning, the tuner will send the generated code to the board and measure the speed of code on the board.
To scale up the tuning, TVM uses RPC Tracker to manage distributed devices. The RPC Tracker is a centralized controller node. We can register all devices to the tracker. For example, if we have 10 phones, we can register all of them to the tracker, and run 10 measurements in parallel, accelerating the tuning process.
To start an RPC tracker, run this command on the host machine. The tracker is required during the whole tuning process, so we need to open a new terminal for this command:
python -m tvm.exec.rpc_tracker --host=0.0.0.0 --port=9190
The expected output is
INFO:RPCTracker:bind to 0.0.0.0:9190
Register Devices to RPC Tracker¶
Now we can register our devices to the tracker. The first step is to build the TVM runtime for the ARM devices.
For Linux: Follow this section Build TVM Runtime on Device to build the TVM runtime on the device. Then register the device to tracker by
python -m tvm.exec.rpc_server --tracker=[HOST_IP]:9190 --key=rk3399
(replace
[HOST_IP]with the IP address of your host machine)For Android: Follow this readme page to install the TVM RPC APK on the android device. Make sure you can pass the android rpc test. Then you have already registered your device. During tuning, you have to go to developer option and enable “Keep screen awake during changing” and charge your phone to make it stable.
After registering devices, we can confirm it by querying rpc_tracker
python -m tvm.exec.query_rpc_tracker --host=0.0.0.0 --port=9190
For example, if we have 2 Huawei mate10 pro, 11 Raspberry Pi 3B and 2 rk3399, the output can be
Queue Status
----------------------------------
key total free pending
----------------------------------
mate10pro 2 2 0
rk3399 2 2 0
rpi3b 11 11 0
----------------------------------
You can register multiple devices to the tracker to accelerate the measurement in tuning.
Set Tuning Options¶
Before tuning, we should apply some configurations. Here I use an RK3399 board
as example. In your setting, you should modify the target and device_key accordingly.
set use_android to True if you use android phone.
#### DEVICE CONFIG ####
# Replace "aarch64-linux-gnu" with the correct target of your board.
# This target is used for cross compilation. You can query it by :code:`gcc -v` on your device.
target = tvm.target.Target("llvm -device=arm_cpu -mtriple=aarch64-linux-gnu")
# Also replace this with the device key in your tracker
device_key = "rk3399"
# Set this to True if you use android phone
use_android = False
#### TUNING OPTION ####
network = "resnet-18"
log_file = "%s.%s.log" % (device_key, network)
dtype = "float32"
tuning_option = {
"log_filename": log_file,
"tuner": "xgb",
"n_trial": 1500,
"early_stopping": 800,
"measure_option": autotvm.measure_option(
builder=autotvm.LocalBuilder(build_func="ndk" if use_android else "default"),
runner=autotvm.RPCRunner(
device_key,
host="127.0.0.1",
port=9190,
number=5,
timeout=10,
),
),
}
Note
How to set tuning options
In general, the default values provided here work well.
If you have enough time budget, you can set n_trial, early_stopping larger,
which makes the tuning run longer.
If your device runs very slow or your conv2d operators have many GFLOPs, considering to
set timeout larger.
If your model has depthwise convolution, you could consider setting
try_spatial_pack_depthwise be True, which perform better than default
optimization in general. For example, on ARM CPU A53 2.0GHz, we find it could boost 1.6x
performance of depthwise convolution on Mobilenet V1 model.
Begin Tuning¶
Now we can extract tuning tasks from the network and begin tuning. Here, we provide a simple utility function to tune a list of tasks. This function is just an initial implementation which tunes them in sequential order. We will introduce a more sophisticated tuning scheduler in the future.
# You can skip the implementation of this function for this tutorial.
def tune_tasks(
tasks,
measure_option,
tuner="xgb",
n_trial=1000,
early_stopping=None,
log_filename="tuning.log",
use_transfer_learning=True,
):
# create tmp log file
tmp_log_file = log_filename + ".tmp"
if os.path.exists(tmp_log_file):
os.remove(tmp_log_file)
for i, tsk in enumerate(reversed(tasks)):
prefix = "[Task %2d/%2d] " % (i + 1, len(tasks))
# create tuner
if tuner == "xgb" or tuner == "xgb-rank":
tuner_obj = XGBTuner(tsk, loss_type="rank")
elif tuner == "xgb_knob":
tuner_obj = XGBTuner(tsk, loss_type="rank", feature_type="knob")
elif tuner == "xgb_itervar":
tuner_obj = XGBTuner(tsk, loss_type="rank", feature_type="itervar")
elif tuner == "xgb_curve":
tuner_obj = XGBTuner(tsk, loss_type="rank", feature_type="curve")
elif tuner == "ga":
tuner_obj = GATuner(tsk, pop_size=50)
elif tuner == "random":
tuner_obj = RandomTuner(tsk)
elif tuner == "gridsearch":
tuner_obj = GridSearchTuner(tsk)
else:
raise ValueError("Invalid tuner: " + tuner)
if use_transfer_learning:
if os.path.isfile(tmp_log_file):
tuner_obj.load_history(autotvm.record.load_from_file(tmp_log_file))
# process tuning
tsk_trial = min(n_trial, len(tsk.config_space))
tuner_obj.tune(
n_trial=tsk_trial,
early_stopping=early_stopping,
measure_option=measure_option,
callbacks=[
autotvm.callback.progress_bar(tsk_trial, prefix=prefix),
autotvm.callback.log_to_file(tmp_log_file),
],
)
# pick best records to a cache file
autotvm.record.pick_best(tmp_log_file, log_filename)
os.remove(tmp_log_file)
Finally, we launch tuning jobs and evaluate the end-to-end performance.
def tune_and_evaluate(tuning_opt):
# extract workloads from relay program
print("Extract tasks...")
mod, params, input_shape, _ = get_network(network, batch_size=1)
tasks = autotvm.task.extract_from_program(
mod["main"], target=target, params=params, ops=(relay.op.get("nn.conv2d"),)
)
# run tuning tasks
print("Tuning...")
tune_tasks(tasks, **tuning_opt)
# compile kernels with history best records
with autotvm.apply_history_best(log_file):
print("Compile...")
with tvm.transform.PassContext(opt_level=3):
lib = relay.build_module.build(mod, target=target, params=params)
# export library
tmp = tempdir()
if use_android:
from tvm.contrib import ndk
filename = "net.so"
lib.export_library(tmp.relpath(filename), ndk.create_shared)
else:
filename = "net.tar"
lib.export_library(tmp.relpath(filename))
# upload module to device
print("Upload...")
remote = autotvm.measure.request_remote(device_key, "127.0.0.1", 9190, timeout=10000)
remote.upload(tmp.relpath(filename))
rlib = remote.load_module(filename)
# upload parameters to device
dev = remote.device(str(target), 0)
module = runtime.GraphModule(rlib["default"](dev))
data_tvm = tvm.nd.array((np.random.uniform(size=input_shape)).astype(dtype))
module.set_input("data", data_tvm)
# evaluate
print("Evaluate inference time cost...")
print(module.benchmark(dev, number=1, repeat=10))
# We do not run the tuning in our webpage server since it takes too long.
# Uncomment the following line to run it by yourself.
# tune_and_evaluate(tuning_option)
Sample Output¶
The tuning needs to compile many programs and extract feature from them. So a high performance CPU is recommended. One sample output is listed below. It takes about 2 hours on a 32T AMD Ryzen Threadripper.
Extract tasks...
Tuning...
[Task 1/12] Current/Best: 22.37/ 52.19 GFLOPS | Progress: (544/1000) | 406.59 s Done.
[Task 2/12] Current/Best: 6.51/ 18.77 GFLOPS | Progress: (608/1000) | 325.05 s Done.
[Task 3/12] Current/Best: 4.67/ 24.87 GFLOPS | Progress: (480/1000) | 372.31 s Done.
[Task 4/12] Current/Best: 11.35/ 46.83 GFLOPS | Progress: (736/1000) | 602.39 s Done.
[Task 5/12] Current/Best: 1.01/ 19.80 GFLOPS | Progress: (448/1000) | 262.16 s Done.
[Task 6/12] Current/Best: 2.47/ 23.76 GFLOPS | Progress: (672/1000) | 563.85 s Done.
[Task 7/12] Current/Best: 14.57/ 33.97 GFLOPS | Progress: (544/1000) | 465.15 s Done.
[Task 8/12] Current/Best: 1.13/ 17.65 GFLOPS | Progress: (576/1000) | 365.08 s Done.
[Task 9/12] Current/Best: 14.45/ 22.66 GFLOPS | Progress: (928/1000) | 724.25 s Done.
[Task 10/12] Current/Best: 3.22/ 15.36 GFLOPS | Progress: (864/1000) | 564.27 s Done.
[Task 11/12] Current/Best: 11.03/ 32.23 GFLOPS | Progress: (736/1000) | 635.15 s Done.
[Task 12/12] Current/Best: 8.00/ 21.65 GFLOPS | Progress: (1000/1000) | 1111.81 s Done.
Compile...
Upload...
Evaluate inference time cost...
Mean inference time (std dev): 162.59 ms (0.06 ms)
Note
Experiencing Difficulties?
The auto tuning module is error-prone. If you always see ” 0.00/ 0.00 GFLOPS”, then there must be something wrong.
First, make sure you set the correct configuration of your device. Then, you can print debug information by adding these lines in the beginning of the script. It will print every measurement result, where you can find useful error messages.
import logging
logging.getLogger('autotvm').setLevel(logging.DEBUG)
Finally, always feel free to ask our community for help on https://discuss.tvm.apache.org